1. Field of the Invention
The present invention generally relates to a photoresist composition, and a method of forming a pattern on a semiconductor device using the same. More particularly, the present invention generally relates to a photoresist composition for forming a photoresist film on a substrate, and a method of forming a photoresist pattern by a photolithography process.
A claim of priority is made to Korean Patent Application No. 2004-37634 filed on May 27, 2004, the content of which is herein incorporated by reference in its entirety.
2. Description of the Related Art
In general, a semiconductor device is fabricated through a series of unit processes such as a layer coating, a patterning of the layer, and a metal wiring.
In general, a semiconductor device pattern is formed by a photolithography process. The photolithography process generally includes a cleaning process, a surface treatment process, a photoresist coating process, an aligning process, an exposing process, and a developing process.
During the photoresist coating process, a photoresist material is coated on a substrate such as a silicon substrate to form a photoresist film. In the aligning process, a photo mask on which an electronic circuit pattern is formed is arranged over the photoresist film. During the exposing process, illuminating light having wavelength to which the photoresist film is sensitive thereto to cause a photochemical reaction is irradiated thereon. Molecular structures of the photoresist film are selectively changed in accordance with the irradiated illuminating light. Then the developing process selectively removes reacted portions of the photoresist film to thereby form a photoresist pattern.
In general, a photoresist material is classified as a positive type and a negative type in accordance with a molecular reaction to light irradiated thereto. When selected areas of the positive photoresist are exposed to light, high molecular compounds of the exposed portions are converted into low molecular compounds, which are more soluble to a developing solution than an unexposed portions thereof. The exposed portions of the photoresist are readily removed from the substrate.
In contrast, when selected areas of the negative photoresist are exposed to light, low molecular compounds are converted into high molecular compounds to thereby have lower solubility to a developing solution than unexposed portions. The unexposed portions of the photoresist are readily removed from the substrate. As a result, the exposed portions remain on the substrate, and the unexposed portions are removed from the substrate after the developing process to thereby form the photoresist pattern.
Subsequently, various underlying layers formed under the photoresist film are selectively removed using the photoresist pattern as an etching mask. Afterwards, the photoresist pattern is removed from the substrate to form a semiconductor pattern on the substrate.
A minimal line width of the photoresist pattern or the semiconductor pattern is determined in accordance with a resolution capability of an exposing system, and the resolution capability of the exposing system is determined by the wavelength of illuminating light. In general, if the resolution of the exposing system is high, the wavelength of the illuminating light is short. That is, a short wavelength of the illuminating light is required to form a fine photoresist pattern.
The resolution of the exposing system is determined by the following equation 1.R=K1NA/λ  (1)
Wherein λ denotes a wavelength of illuminating light; R denotes a resolution limit of the exposing system; K1 denotes a proportional constant; and, NA denotes a numerical aperture for a lens used in the exposing system. According to equation (1), wavelength λ of the illumination light and proportional constant K1 must be small, and the numerical aperture of the lens must be large to increase the resolution of the exposing system. Among these factors, changing wavelength λ is most widely utilized to increase the resolution of the exposing system.
Examples of the illumination light include a G-line light having a wavelength of about 436 nm, an I-line light having a wavelength of about 365 nm, a deep ultraviolet (DUV) light having a wavelength of about 248 nm, and an argon fluoride (ArF) light having a wavelength of about 193 nm. Although the DUV light includes a KrF light as well as the ArF light in view of the optical technology, the KrF light will be referred to as the DUV light in the present specification. The KrF light has a wavelength of about 248 nm.
U.S. Pat. Nos. 6,121,412 and 5,521,052, for example, disclose photoresist compositions having good solubility and maintenance stability without precipitation of photosensitive ingredients.
In general, a photoresist composition includes a polymer, a quencher, a photo acid generator, and a photoresist solvent.
The polymer, which is widely referred to as a resin, is a chemical compound in which two or more monomers combine to form compound molecules that contain repeating structural units. The polymer is the residual substance of the photoresist pattern remaining after the developing process. Light dissolves photo acid generator in the photoresist solvent. The photo acid functions as a catalyst during a chemical reaction to convert the molecular structure of the polymer. The photoresist solvent is a mixture of polar and non-polar solvents. The photoresist solvent also controls viscosity of the photoresist composition.
DUV light and ArF light have been frequently utilized to manufacture highly integrated and high performing semiconductor devices. As described above, the photoresist composition sensitive to the DUV light (DUV photoresist composition) is quite different from the photoresist composition sensitive to the ArF light (ArF photoresist composition). However in general, the solvents used for the DUV photoresist composition and the ArF photoresist composition are substantially the same.
The ArF photoresist composition has relatively poor solubility as compared with the DUV photoresist composition when using the same solvents, because the ArF photoresist composition is hydrophobic. Accordingly, when the ArF photoresist film is exposed to air, the resin dissolved in the solvent precipitates in very short time. The precipitated resin gathers around an injection nozzle and is injected onto a surface of a substrate during a coating process. The precipitated resin causes defects on the substrates.
The precipitated resin is a problem that must be solved to further the developments in the manufacturing of the semiconductor device.